1. Field of the Invention
This invention relates to a method for the manufacture of a flexible printed wiring board by plating, particularly to a method for the manufacture of printed coils.
2. Description of the Prior Art
In the pattern plating method, it is difficult to maintain an adequate balance between the tight adhesion of a plating resist and a conductor circuit to a metallic board during the course of plating and the peeling property thereof from the metallic board during the course of transfer. The plating conductor circuit and the plating resist are required to remain intimately or firmly adhering to the metallic board during the course of the printing. When this adhesion is excessively tight, the separation from the metallic board during the course of transfer is obtained with difficulty. There even ensues a possibility that part of the conductor circuit and the plating resist will remain on the metallic board, rendering desired transfer difficult to obtain. When the separation during the transfer is enabled to occur easily, the plating resist readily peels, making production of satisfactory pattern difficult to obtain.
Enhancement of adhesion is obtained by coarsening the surface of the metallic board and facilitation of separation by applying on the surface of the metallic board a release agent such as, for example, silicone oil, wax, colloidal graphite, stearic acid of a salt thereof. By these measures, however, the range in which a printed wiring board of high quality is obtained is limited. These measures admit of a variety of causes for dispersion of product quality and permit production of a satisfactory printed wiring board with great difficulty.
As means of producing a printed wiring board by the electric pattern plating technique, Japanese Patent Application Laid-open No. SHO 58(1983)-9397 discloses a method which comprises laminating a dry film of photosensitive resin on a metallic board, exposing the dry film through a mask of a given wiring pattern, developing and post-baking the exposed dry film thereby forming a resist, electroforming copper on the exposed portion of the surface of the metallic board in a thickness not exceeding the thickness of the dry film, separating the resultant electroformed pattern of copper from the metallic board, and applying it fast on an insulating substate. In the disclosure of this method, however, nothing is mentioned about any means of fully satisfying the two requirements, tight adhesion during the course of electroforming and easy separation after the electroforming.